An Ethernet network operator supplies connections across their Ethernet transport network to a customer (hereinafter referred to as the user). When a user buys a connection they will typically negotiate a Service Level Agreement (SLA), which defines various parameters and limits of the connection. For example, the following elements may be defined. The Committed Information Rate (CIR), which is the average data bandwidth in Mbits/s that is guaranteed to be transported. The Peak Information Rate (PIR), which is the average peak information rate in Mbits/s that is available between the various users. The Committed Burst Size (CBS), which is specified in bytes and denotes the maximum number of bytes available for a burst of ingress data at the UNI (User to Network Interface) speed to remain CIR conformant. The Peak Burst Size (PBS), which is specified in bytes and denotes the maximum number of bytes available for a burst of ingress data at the UNI speed to remain PIR conformant.
Hereinafter the network connection provided by the network operator to a user will be referred to as the service.
It is highly desirable that the network operator is able to obtain an accurate and representative historical record of the user's service usage with respect to the SLA. Such information would allow the network operator to determine when a user has breached their SLA and would also allow the operator to manage their network effectively.
There are known monitoring systems that gather statistics with respect to the utilisation of a physical link. However, these systems only provide a value representing the average utilisation over a defined period of time. These systems are useful in certain circumstances, although they do not provide information of sufficient detail or resolution to allow the network operator to determine whether the user is adhering to the SLA.
Ideally the network operator wants to have a continuous record of the utilisation of the service imposed by the user sampled every few seconds. However, as a network operator must supply services to a multitude of distinct customers, such an approach would exert an exorbitant cost on the operator in terms of memory requirements.